Deposition methods are utilized for forming films of material across substrate surfaces. Deposition methods can be utilized in, for example, semiconductor fabrication processes to form layers ultimately utilized in fabrication of integrated circuitry structures and devices. An exemplary deposition method is physical vapor deposition (PVD), which includes sputtering processes.
A physical vapor deposition operation is described with reference to a sputtering apparatus 110 in FIG. 1. Apparatus 110 is an example of an ion metal plasma (IMP) apparatus, and comprises a chamber 112 having sidewalls 114. Chamber 112 is typically a high vacuum chamber. A target 10 is provided in an upper region of the chamber, and a substrate 118 is provided in a lower region of the chamber. Substrate 118 is retained on a holder 120, which typically comprises an electrostatic chuck. Target 10 would be retained with suitable supporting members (not shown), which can include a power source. An upper shield (not shown) can be provided to shield edges of the target 10.
Substrate 118 can comprise, for example, a semiconductor wafer, such as, for example, a single crystal silicon wafer. A metal-containing film can be over a surface of the substrate in particular applications. Target 10 can comprise, for example, one or more of nickel, tantalum, titanium, copper, aluminum, silver, gold, niobium, platinum, palladium, tungsten and ruthenium, including one or more alloys of the various metals. Exemplary targets can comprise one or more of various mixtures, compounds or alloys including, for example, Ti/N, Ti/Nb, Ti/W and Ti/Al. The target can be a monolithic target, or can be part of a target/backing plate assembly.
Material is sputtered from a surface of target 10 and directed toward substrate 118. The sputtered material is represented by arrows 122.
Generally, the sputtered material will leave the target surface in a number of different directions. This can be problematic, and it is preferred that the sputtered material be directed relatively orthogonally to an upper surface of substrate 118. Accordingly, a focusing coil 126 is provided within chamber 112. The focusing coil can improve the orientation of sputtered materials 122, and is shown directing the sputtering materials relatively orthogonally to the upper surface of substrate 118.
Coil 126 is retained within chamber 112 by pins 128 which are shown extending through sidewalls of the coil and also through sidewalls 114 of chamber 112. Pins 128 are retained within retaining screws 132 in the shown configuration. The schematic illustration of FIG. 1 shows heads 130 of the pins along the exterior surface of chamber sidewalls 114, and another set of heads of the retaining screws 132 along an interior surface of coil 126.
Spacers 140 extend around pins 128, and are utilized to space coil 126 from sidewalls 114.
Problems can occur in deposition processes if particles are formed, in that the particles can fall into a deposited film and disrupt desired properties of the film. Accordingly, it is desired to develop traps which can alleviate problems associated with particles falling into a desired material during deposition processes.
Some efforts have been made to modify PVD targets to alleviate particle formation. For instance, bead blasting has been utilized to form a textured surface along sidewalls of a target with the expectation that the textured surface will trap particles formed along the surface. Also, knurling and machine scrolling have been utilized to form textures on target surfaces in an effort to create appropriate textures that will trap particles.
Although some of the textured surfaces have been found to reduce particle formation, the particle formation is frequently not reduced to a desired level. In some instances, the texturing on a sidewall surface of a target can ultimately lead to formation of very large particles. Specifically, films of sputtered material form on the textured surface over time, and at some point the films peel away from the target. The films can fall onto a substrate during a PVD process to cause a defect in a layer deposited during the PVD process. This problem is frequently encountered with textures which have been formed through machine scrolling and/or knurling.
Another problem is that the formation of a textured surface can itself introduce contaminants. For instance, bead-blasting typically utilizes particles blasted at the target with high energy to texture a surface of the target. Some of the particles from for the blasting can be imbedded in the target during the blasting process, remain with the target as it is inserted in a PVD chamber, and then fall from the target during a sputtering process to become problematic contaminants during the sputtering.
It would be desired to develop a new texture which can be formed on sidewalls or other non-sputtered surfaces of a PVD target construction to better alleviate particle formation than prior art textures, and it would be particularly desirable if the new texture could eliminate undesired peeling of materials from sidewalls and other non-sputtered surfaces of a target construction during PVD processing. It would also be desired to reduce, and preferably eliminate sputtering process contamination resulting from embedded bead-blasted particles in sputtering target constructions.